Hypertension is the number one cause of racial group disparities in mortality in the U.S. Thus, understanding the mechanisms by which race is linked with the cardiovascular system is key. African Americans (AA) are exposed to more stress across the lifespan and lifetime adversity is associated with cardiovascular disease (CHD) and hypertension. However, mechanisms accounting for the links between long-term stress exposure, hypertension and CHD remain unclear. Cardiovascular reactivity is hypothesized to be a major contender as it predicts increased risk of cardiac events and mortality, especially among people with hypertension. According to existing theories of racial health disparities, stress, and social relations, racial health disparities are due to variations in long-term exposure to stress and stress reactivity (biological, psychological, behavioral) and those race differences are moderated by social relations and age. In response to the FOA Aging Research on Stress and Resilience to Address Health Disparities in the United States (RFA-AG-16-022), the present study seeks to understand how long-term stress exposure links with stress reactivity among AA and EA adults. This study capitalizes the existing longitudinal Social Relations and Health Study (SRS),a regionally representative panel sample of AA and EA individuals from the Detroit metropolitan area who began participating in 1992 (ages 13 to 93) and completed the third wave in 2015 (ages 30 to 95). The proposed study will incorporates two new studies of short-term stress reactivity: 1) a daily stress study and 2) a laboratory stress study. The daily stress study will target 300 participants (50% AA; 50%EA) and will incorporate a 4 day experience sampling study of self-reported stress exposure and reactivity (psychological, behavioral) as well as two ambulatory monitoring devices to assess biological reactivity: 1) a newly developed non-invasive continuous monitoring ring device that provides estimates of vascular resistance and 2) a watch that assesses heart rate, heart rate variability, and galvanic skin response. In the laboratory study we will examine reactivity to standard laboratory stressors among a sample of 50 AA and 50 EA respondents who completed the daily stress study to examine more thoroughly their physiological responses to stress with the same ambulatory ring and watch as well as established continuous monitors. The proposed research addresses three aims: 1) Test links between long- term stress exposure and short-term stress reactivity among EA and AA adults, 2) Examine age differences in long-term stress exposure and short-term reactivity by race, and 3) Determine how long-term social relationships moderate individual differences in stress exposure and reactivity. This project has public health significance as it will identify individuals who are more reactive to stress and the immediate as well as lifespan factors that are associated with greater stress reactivity. A more nuanced understanding of the psychological and biological implications of stress among diverse populations will lead to the development and testing of interventions for reducing stress, later health problems, and health disparities.